Transalkylation of alkylaromatic hydrocarbons in contact with a zeolite catalyst composition

ABSTRACT

A PROCESS FOR THE TRANSALKYLATION OF ALKYLAROMATIC HYDROCARBONS. TRANSALKYLATION OF ALKYLAROMATIC HYDROCARBONS, SUCH AS TOLUENE, IS EFFECTED AT TRANSALKYLATION CONDITIONS IN CONTACT WITH A CATALYST COMPRISING FROM ABOUT 60 TO ABOUT 90% OF A ZEOLITE HAVING A MORDENITE CRYSTAL STRUCTURE CONTAINING ALUMINA FIXED IN COMBINATION THEREWITH. THE CATALYST IS CHARACTERIZED BY A METHOD OF PREPARATION.

United States Patent C TRANSALKYLATION F ALKYLAROMATIC HY- DROCARBONS DJCONTACT WITH A ZEOLITE CATALYST COMPOSITION Roy T. Mitsche, Island Lake,and Edward Michalko,

Lombard, Ill., assignors to Universal Oil Products Company, Des Plaines,Ill.

No Drawing. Continuation-impart of application Ser. No. 20,024, Mar. 16,1970. This application Mar. 27, 1972, Ser. No. 238,622

Int. Cl. C07c 3/62 US. Cl. 260-672 T 8 Claims ABSTRACT OF THE DISCLOSUREA process for the transalkylation of alkylaromatic hydrocarbons.Transalkylation of alkylaromatic hydrocarbons, such as toluene, iseffected at transalkylation conditions in contact with a catalystcomprising from about 60 to about 90% of a zeolite having a mordenitecrystal structure containing alumina fixed in combination therewith. Thecatalyst is characterized by a method of preparation.

This application is a continuation-in-part of a copending applicationSer. No. 20,024, filed Mar. 16, 1970.

Crystalline aluminosilicates, or zeolites, are well known in the art andhave found extensive application as hydrocarbon conversion catalysts oras a component thereof. Such materials are of an ordered crystallinestructure comprising cages or cavities interconnected by smaller poresand channels of a definite size range characteristic of each crystallinealuminosilicate variety. Since the dimensions of the pores and channelsare such as to accept molecules of certain dimension while rejectingthose of larger dimension, these materials have come to be known asmolecular sieves and utilized in many ways taking advantage of theseproperties.

The crystalline aluminosilicates, hereinafter referred to as zeolites,are generally described as a three-dimensional network of fundamentalstructural units consisting of silicon-centered SiO andaluminum-centered AlL tetrahedral interconnected by a mutual sharing ofapical oxygen atoms. To effect a chemical balance, each A10 tetrahedrahas a cation associated therewith, usually sodium. In most cases, thecation is subsequently exchanged with a hydrogen ion to yield thehydrogen or active form of the zeolite.

The SiO and A10 tetrahedra are arranged in a definite geometric patternoften visualized either in terms of chains, layers or polyhedra, allformed by the linking of the tetrahedra. In any case, the zeolitescomprise Welldefined intracrystalline dimensions includingintracrystalline channels and pore openings whose narrowest crosssection has essentially a uniform diameter. The various zeolites may beclassified according to the geometric pattern of their framework withits attendant pore size, and by the Si0 /Al O mole ratio of theircomposition.

Mordenite is a particular zeolite, highly siliceous in nature, andgenerally characterized by a SiO /Al- O mole ratio of from about 6 toabout 12 as manufactured or found in its natural state. The mordenitecrystal structure comprises four and five membered rings of $0,, and A10tetrahedra so arranged that the resulting crystal lattice comprisespores and channels running parallel along the crystal axis to give atubular configuration. This structure is unique among the zeolites sincethe channels or tubes do not intersect and access to the cages orcavities is in only one direction. For this reason, the mordenitestructure is frequently referred to as twodimensional. This is incontrast to other well-known Patented Mar. 13, 1973 zeolites, forexample faujasite and Zeolite A, in which the cages can be entered fromthree directions.

Conventional mordenite exhibits an unusual acid stability attributed toits siliceous nature, and the SiO Al O mole ratio of conventionalmordenite can be further increased to as much as 50:1 or more by thetechnique of acid-leaching alumina therefrom While maintaining themordenite crystal structure. Compositions comprising mordenite, causticand acid extracted mordenite, mordenite supported on or dispersed in acarrier material, and other variations and combinations of mordenite,have been prepared, often as catalysts for specific hydrocarbonconversion reactions. However, the art has not heretofore disclosed thecatalyst composition of this invention comprising a zeolite having themordenite crystal structure and containing alumina fixed in combinationtherewith. Other zeolites having the mordenite crystal structure and ofsubstantially the same SiO /Al O mole ratio as herein contemplated, canbe prepared by prior art methods, eg leaching of alumina fromconventional mordenite. However, said zeolites do not yield the improvedcatalyst composition of this invention. Thus, the catalyst compositionof this invention is characterized by a method of preparation, thenovelty and utility of the catalyst composition being evidenced by itsextraordinary activity and stability as a catalyst with respect to thetransalkylation or disproportionation of alkylaromatic hydrocarbons.

The transalkylation or disproportionation of alkylaromatic hydrocarbonsis of particular importance in conjunction with catalytic reforming. Inrecent years, largely due to the success and growth of catalyticreforming and improved methods of separating and recovering aromatichydrocarbons produced thereby, the petroleum industry has become aprincipal source of benzene, toluene, and other aromatic andalkylaromatic hydrocarbons. The supply and demand for specific aromatichydrocarbons varies from time to time. For example, it is not uncommonto find toluene in excess of demand while benzene is in short supply. Toobviate this situation, it is desirable to treat the toluene attransalkylation or disproportionation reaction conditions whereby onemolecule is alkylated at the expense of another molecule which isdealkylated to yield benzene and xylenes or other polymethylatedbenzenes.

'It is an object of this invention to present an improved process forthe transalkylation of alkylaromatic hydrocarbons utilizing the novelcomposition as a catalyst therefor.

In one of its broad aspects, the present invention embodies a processfor the transalkylation of an alkylaromatic hydrocarbon which comprisestreating an alkylaromatic hydrocarbon having from about 7 to about 15carbon atoms per molecule in admixture with from about 1 to about 10moles of hydrogen per mole of hydrocarbon at transalkylation conditionsincluding a temperature of from about 200 to about 480 C., in contactwith a catalyst comprising from about 60 to about wt. percent of azeolite having a mordenite crystal structure and containing aluminafixed in combination therewith, said catalyst composition having beenprepared by (l) heating an amorphous silica-alumina composite at atemperature of from about to about 250 C. in a closed vessel inadmixture with an aqueous alkali metal solution, said composite beingcharacterized by a SiO A1 0 mole ratio of from about 10 to about 30, andsaid solution having an alkali metal concentration sufiicient to providean alkali metal/aluminum ratio of from about 1.5 to about 3.5, andforming a zeolite with a mordenite crystal structure and ofsubstantially the same Si0 A1 0 mole ratio as the amorphoussilica-alumina starting material, and (2) heating said zeolite in analumina sol, thereafter separating excess sol, treating the zeolite-solproduct at conditions effecting gelation of the sol, aging the resultingcomposition in an alkaline media for a period of at least about hoursand washing, drying and calcining. Other objects and embodiments of thisinvention Will become apparent With reference to the following detailedspecification.

In the manufacture of the catalyst composition of this invention, thezeolite component is initially prepared to comprise a Slo /A1 0 moleratio of from about 12 toabout 30, and preferably from about 15 to about25. This is in contrast to conventional mordenite, either naturallyoccurring or synthetically prepared, which is generally characterized bya SiO /Al O mole ratio of from about 6 to about 12. The zeolite hereinemployed is initially prepared to comprise the desired SiO /Al O moleratio by utilizing an amorphous silica-alumina composite as a startingmaterial, the amorphous silica-alumina composite being of substantiallythe same SiO /Al O mole ratio as that desired in the zeolite product. Aconvenient source of amorphous silica-alumina starting material isconventional amorphous silica-alumina cracking catalyst of less thanabout 13 wt. percent alumina. Said catalyst is typically manufactured bya series of process steps involving initially the formation of an acidicsilica sol by acidification of an aqueous sodium silica solution (Waterglass). It has been observed that silica-alumina, wherein the silica hasbeen derived from an acidic silica sol, gives an improved rate ofreaction in the formation of the zeolite as herein contemplated.Subsequent process steps in the manufacture of said cracking catalystinclude gelation of the silica sol after which the resulting slurry isadjusted to a pH of about 3.5 and impregnated with an aluminum saltsolution, usually an aqueous aluminum sulfate solution, the aluminumsulfate being thereafter hydrolyzed and precipitated. The silica-aluminaproduct is commonly slurried with water and spray-dried to yield finesilica-alumina microspheres particularly suitable as a starting materialin the manufacture of the zeolite component of the catalyst compositionof this invention.

While an amorphous silica-alumina composite wherein the silica isderived from an acidic silica sol is preferred, an amorphoussilica-alumina composite wherein the silica is derived from a basicsilica sol may also be utilized. For example, silica-alumina cogels areoften prepared by admixing an aqueous sodium silicate solution or solwith an acidic aluminum sulfate solution to form a sol blend with a pHin excess of about 7. The blend is substantially immediately dispersedas droplets in a hot oil bath, aged therein at elevated temperature,water-washed, dried and calcined.

Regardless of the derivation of the amorphous silicaalumina startingmaterial, the silica-alumina composite is heated in admixture with anaqueous alkali metal solution at a temperature of from about 140 toabout 250 C. in a closed vessel. The alkali metal solution has an alkalimetal concentration sufficient to provide an alkali metal/aluminum ratioof from about 1.5 to about 3.5 in the reaction mixture. The alkali metalis usually sodium, the alkali metal solution being suitably an aqueoussodium hydroxide solution. Zeolite yields of 90-100% are obtained afterthe stirred reaction mixture has been heated for a period of from about8 to about 24 hours. The zeolite product thus prepared is characterizedby a SiO A1 0 mole ratio substantially the same as the amorphoussilica-alumina starting material. While the zeolite may be converted tothe hydrogen form by conventional ionexchange techniques prior totreating with the alumina sol, no particular improvement resultstherefrom and the zeolite is suitably and conveniently utilized in thesodium form.

As will become apparent with reference to the method of preparationhereinafter presented, the composition of this invention comprises azeolite having a mordenite crystal structure and containing aluminafixed in physical and/or chemical combination therewith in contrast tothe conventional practice of suspending the zeolite in a refractoryoxide. Thus, the present invention does not contemplate the presence ofany substantial amount of extraneous alumina in the claimed composition.In another embodiment of this invention relating to a method ofpreparing said composition, the zeolite, characterized by a SiO /Al Omole ratio of from about 10 to about 30 and pore openings of from about3 to about 8 angstroms, is heated in admixture with an alumina sol, saidzeolite being admixed with said sol prior tobeing dried at a temperaturein excess of about 300 C. The supernatant or extraneous sol isthereafter separated and the zeolitealumina sol product treated atconditions effecting gelation of the sol. The zeolite-alumina gelproduct is thereafter aged in an alkaline medium, washed and dried.

The zeolite is suitably heated in admixture with the alumina sol at atemperature of from about 50 to about 150 C. at conditions to obviateany substantial loss of water. Thus, the zeolite and alumina sol may beheated together in a closed vessel. Preferably, the zeolite and aluminasol are heated together at a temperature of from about to about 125 C.for a period of at least about 10 hours, and preferably at a temperatureof from about 75 to about 125 C. for a period of from about 20 to abouthours. The alumina sol is preferably, although not necessarily, analuminum chloride sol such as is prepared by digesting aluminum metal inan acidic reagent such as hydrochloric acid and/ or aqueous aluminumchloride at about the boiling point of the mixture-usually a temperatureof from about 80 to about C. However, alumina sols derived from otheraluminum salts such as aluminum sulfate, aluminum nitrate, sodiumaluminumate, etc., can be employed.

The supernatant or extraneous alumina sol is decanted, filtered orotherwise separated from the zeolite-alumina sol product which issubsequently treated at conditions effecting gelation of the reactedsol. Preferably, the zeolite-alumina sol product is treated in contactwith an aqueous ammonia solution whereby gelation of the sol occurs andthe zeolite-gel product aged for a period of at least about 5 hours andpreferably for a period of from about 10 to about 24 hours in thealkaline solution to achieve optimum activity of the final catalystcomposition. The resulting zeolite-alumina gel product is usuallyWaterwashed and dried at a temperature of from about 95 to about 300 C.for a period of from about 2 to about 24 hours or more. The driedzeolite-alumina gel product may then be pilled or extruded using knowntechniques to obtain particles of the desired shape or size.

When the composition is to be employed as a catalyst, it isadvantageously further calcined at a temperature of from about 400 toabout 600 C. in an air atmosphere for a period of from about 0.5 toabout 10 hours. The activity of the composition as a catalyst is favoredby calcination in air containing from about 1 to about 5 wt. percentwater at a temperature of from about 400 to about 600 C., and thereafterin a substantially dry atmosphere at said temperature.

It has been found that when, as aforesaid, zeolite is admixed with thealumina sol prior to being dried at a temperature in excess of about 300C. and preferably prior to being dried at a temperature in excess ofabout C., so as to retain volatile matter in excess of about 15%, thezeolite embodies a peculiar affinity for alumina not otherwise observed.This peculiar affinity is evidenced by a greater capacity of the zeolitefor alumina fixed in physical and/ or chemical combination therewith asherein contemplated. The peculiar affinity is further evident from thecatalytic effect of the composition with respect to the aforementionedtransalkylation reaction-a more than twofold increase in activity andstability being realized.

The present invention further embodies a process which comprisestreating an aromatic hydrocarbon having from about 7 to about 15 carbonatoms per molecule at transalkylation conditions including a temperatureof from about 200 to about 480 C. and a pressure of from aboutatmospheric to about 1500 pounds per inch gauge (p.s.i.g.) in contactwith a catalyst comprising essentially the composition of this inventionand forming products of higher and lower number of carbon atoms thansaid alkylaromatic hydrocarbon. The preferred composition employed as acatalyst comprises a zeolite having the mordenite crystal structure andcontaining alumina fixed in combination therewith, said zeolitecomprising from about 50 to about 75 wt. percent of said composition.

The alkylaromatic hydrocarbon feed stock treated in accordance with thepresent process can be a substantially pure alkylaromatic hydrocarbon offrom about 7 to about 15 carbon atoms, a mixture of such alkylaromatichydrocarbons or a hydrocarbon fraction rich in said alkylaromatics.Suitable alkylaromatic hydrocarbons include alkylbenzenes andalkylnaphthalenes, preferably with an alkyl group of less than about 4carbon atoms. The process is particularly applicable to the treatment ofthe more difficultly transalkylatable toluene to form benzene andxylenes or other polymethylbenzenes.

The transalkylation, or disproportionation, reaction of this inventioncan be effected in contact with the catalyst composition of thisinvention in any conventional or otherwise convenient manner and maycomprise a batch or continuous type operation. A preferred type ofoperation is of the continuous type. For example, the above-describedcatalyst is disposed in a fixed bed in a reaction zone of a verticaltubular reactor and the alkylaromatic feed stock charged in an upflow ordownflow manner, the reaction zone being maintained at a temperature offrom about 200 to about 480 C., preferably at a temperature of fromabout 220 to about 460 C. While pressure does not appear to be animportant variable with respect to the transalkylation reaction of thisinvention, the process is generally conducted in a presence of animposed hydrogen pressure to provide from about 1 to about 10 moles ofhydrogen per mole of hydrocarbon. However, there is no net consumptionof hydrogen in the process, and the hydrogen charge is recovered fromthe reactor effluent and recycled.

The transalkylation reaction can be effected over a wide range of spacevelocities. In general, the process is conducted at a space velocity offrom about 0.2 to about 10. Space velocities herein referred to areliquid hourly space velocities, (LHSV) i.e., volume of charge per volumeof catalyst per hour. While the present process is characterized byunusually high space velocities indicative of high activity, it isparticularly noteworthy because of its relatively high stability of thecatalyst at a high activity level.

The composition herein disclosed may be employed as a component of acatalyst comprising any of the several catalytically active metallicmaterials in the oxidized or reduced state. Of particular interest arethose catalytic composites comprising one or more metals of Group VIBand VIII including molybdenum, tungsten, chromium, iron, nickel, cobalt,platinum, palladium, ruthenium, rho dium, osmium and iridium. Thus, thecomposition of this invention can be utilized advantageously as acatalyst or component thereof to effect a variety of hydrocarbonconversion reactions involving reaction conditions comprising atemperature in the 70-1400" F. range. The catalysts are particularlyuseful in effecting the hydrocracking of heavy oils, including vacuumresiduals, to form petroleum products in the middle distillate rangeutilizing a temperature of from about 500 to about 3000 F. and pressuresof from about 500 to about 1000 p.s.i.g. Said hydrocarbon conversionreactions further include polymerization of olefins, particularlyethylene, propylene, l-butene, 2-butene, isobutylene and also higherboiling olefins, at polymerization reaction conditions. The compositionof this invention is also useful as a catalyst or component thereof ineffecting the alkylation of isoparaflins with olefins or otheralkylating agents including, for example, alkylhalides and the like; andalso the alkylation of isobutane, isopentane, and/ or isohexane withethylene, propylene, l-butene, etc., or mixtures thereof; and also thealkylation of aromatics with olefins or other alkylating agents,particularly the alkylation of benzene, toluene, etc., with propylene,butylene, and higher boiling olefins including nonenes, decenes,undecenes, etc., the foregoing alkylation reactions being effected atalkylation conditions disclosed in the art. The composition of thisinvention is further useful in the isomerization of paraffins,particularly n-butane, n-pentane, n-hexane, n-heptane, n-octane, etc.,or mixtures thereof, including isomerization of less highly branchedchain saturated hydrocarbons to more highly branched chain saturatedhydrocarbons such as the isomerization of 2- or 3-methylpentane to 2,2-and 2,3-dimethylbutane, isomerization of naphthenes, for example, theisomerization of dimethylcyclopentane to methylcyclohexane,isomerization of methylcyclopentane to cyclohexane, etc. atisomerization reaction conditions. Other hydrocarbon conversionreactions including the reforming of naphtha to gasoline,dehydrogenation of ethylbenzene to styrene, and the hydrogenation ofbenzene to cyclohexene, are effectively catalyzed utilizing thecomposite of this invention as a catalyst or component thereof.

The following examples are presented in illustration of the presentinvention and are not intended as an undue limitation on the generallybroad scope of the invention as set out in the appended claims.

EXAMPLE I In the manufacture of the zeolite component of the catalystcomposition of this invention, an amorphous silica-alumina,characterized by a SiO /Al O mole ratio of 20.0, was utilized as astarting material. The amorphous material was prepared by theacidification of 23.6 liters of 6.9% aqueous water glass solution with2.99 liters of 25% sulfuric acid, the final pH being about 4.3. Gelationoccurred in about 10 minutes, and 175 cc. of a 15% aqueous ammoniasolution was added to the resulting slurry to adjust the pH to about7.7, the temperature being maintained at about 35 C. After about onehour, 200 cc. of 25 sulfuric acid was added lowering the pH to 6.5. Apreneutralized aluminum sulfate solution, prepared by blending 700 cc.of a 28% aqueous ammonia solution with 2800 cc. of an aqueous aluminumsulfate solution (comprising the equivalent of 6.7 wt. percent A1 0 wasadded to the aqueous silica slurry with stirring, the pH being furtherlowered to about 3.9. Hydrolysis of the aluminum sulfate was effected ata pH of about 6.5 by the addition of 810 cc. of a 15% aqueous ammoniasolution. After one hour at said pH, the mixture was filtered,reslurried in water and spray-dried.

450 grams of the spray-dried silica-alumina microspheres (400 gramsV.F., 7.83 wt. percent A1 0 were admixed with 57.0 grams of sodiumhydroxide in aqueous solution (1500 cc.) and sealed in an autoclave. Theautoclave was rotated and heated to a temperature of 200 C. over atwo-hour period and further rotated and heated at 200 C. for 12 hours.The reaction mixture was cooled and filtered to recover the solidsproduct. The product was washed and dried in the described manner. X-rayanalyses indicated the product to be zeolite with a SiO /Al O mole ratioof 19.7 and a mordenite crystal structure.

About grams of said zeolite was heated in about 700 cc. of an aluminumchloride hydrosol using a glass vessel equipped with an overhead refluxcondenser. The aluminum chloride hydrosol comprised 12.49 wt. percentalumina, 10.75 wt. percent chloride, and had a specific gravity of1.3630. The mixture was heated for about 24 hours at reflux conditions(95100 C.). Thereafter, the zeolite sol product was recovered byfiltration. The zeolitesol product included about 270 cc.'(86.4 grams A10 of sol. The zeolite-sol product was slurried with a 15 aqueous ammoniasolution for about one hour and aged in the solution overnight at 95 C.The resulting zeolitegel product was thereafter further Washed withdilute aqueous ammonia until the filtrate was chloride-free. The productwas oven-dried at 110 C., pilled and calcined. Calcination consisted inheating the product in air containing 3% water for one hour at 550 C.and thereafter in dry air for one hour at 550 C. X-ray analysisindicated the final product to comprise 50 Wt. percent zeolite of themordenite crystal structure and 42% alumina.

EXAMPLE II The activity and stability of the catalyst composition ofExample I was determined with respect to the transalkylation of toluene.The toluene was charged downfiow in contact with the catalystcomposition at a liquid hourly space velocity of about 5 and attransalkylation conditions including a pressure of 500 p.s.i.g., atemperature of 420 C. and a hydrogen to hydrocarbon ratio of 10. Thecatalyst bed measured 50 cc. of inch pills. During an initial testperiod of about hours, a 50% conversion of toluene per pass wasachieved. The product included 50 wt. percent unconverted toluene, 20wt. per cent benzene, 23 Wt. percent xylene, and 4.5 wt. percent Chydrocarbons. After approximately 90 hours on stream, a catalystsampling indicated 0.29 wt. percent carbon on the catalyst. After about184 hours on stream at approximately the same transalkylationconditions, the toluene conversion and the product distribution wassubstantially unchanged.

We claim as our invention:

1. A process for the transalkylation of alkylaromatic hydrocarbons whichcomprises treating an alkylaromatic hydrocarbon having from about 7 toabout carbon atoms per molecule in admixture with from about 1 to about10 moles of hydrogen per mole of hydrocarbon at transalkylationconditions, including a temperature of from about to about 480 C., incontact with a catalyst comprising from about 60 to about 90 wt. percentof a zeolite having a mordenite crystal structure and containing aluminafixed in combination therewith, said catalyst having been prepared by(1) heating an amorphous silica-alumina composite at a temperature offrom about 140 C. to about 250 C. in a closed vessel in admixture withan aqueous alkali metal solution, said composite being characterized bya SiO /Al O mole ratio of from about 10 to about 30, and said solutionhaving an alkali metal concentration sufiicient to provide an alkalimetal/ aluminum ratio of from about 1.5 to about 3.5, and forming azeolite with a mordenite crystal structure and of substantially the sameSiO /Al O mole ratio as the amorphous starting material, and (2) heatingsaid zeolite in an alumina sol, thereafter separating excess sol,treating the zeolite-sol product at conditions effecting gelation of thesol, aging the resulting composition in an alkaline media for at leastabout five hours, and washing, drying and calcining the aged composite.

2. The method of claim 1 further characterized in that the alkylsubstituent of said alkylaromatic hydrocarbon comprises less than 4carbon atoms.

3. The method of claim 1 further characterized in that saidalkylaromatic hydrocarbon is toluene.

4. The method of claim 1 further characterized in that saidtransalkylation conditions include a temperature of from about 220 toabout 460 C.

5. A process for the transalkylation of an alkylaromatic hydrocarbonwhich comprises treating an alkylaromatic hydrocarbon having from about7 to about 15 carbon atoms per molecule in admixture With from about 1to about 10 moles of hydrogen per mole of hydrocarbon at transalkylationconditions, including a temperature of from about 200 to about 480 C.,in contact with a catalyst comprising from about to about wt. percent ofa zeolite having a mordenite crystal structure and containing aluminafixed in combination therewith, said catalyst having been prepared by(1) heating an amorphous silica-alumina composite at a temperature offrom about 140 C. to about 250 C. in a closed vessel in admixture withan aqueous sodium hydroxide solution, said composite being characterizedby a SiO /Al O mole ratio of from about 12 to about 25, and saidsolution having a sodium concentration suflicient to provide asodium/alumina ratio of from about 1.5 to about 3.5, and forming azeolite with a mordenite crystal structure and of substantially the sameSiO /Al O mole ratio as the amorphous starting material, (2) heatingsaid zeolite in an alumina chloride sol at a temperature of from about75 to about 125 C. for a period of from about 20 to about hours prior tosaid zeolite being dried at a temperature in excess of about 300 C.,thereafter separating excess sol, treating the zeolite-sol product atconditions eifecting gelation of the sol, aging the resultingcomposition in an aqueous ammonia solution for from about 10 to about 24hours at a temperature of from about 75 to about 100 C., and washing,drying and calcining the aged composition at a temperature of from about400 to about 600 C. in air containing from about 1 to about 5 wt.percent water, and thereafter in a substantially dry atmosphere at saidtemperature of from about 400 to about 600 C.

6. The method of claim 5 further characterized in that the alkylsubstituent of said alkylaromatic hydrocarbon comprises less than about4 carbon atoms.

7. The method of claim 5 further characterized in that saidalkylaromatic hydrocarbon is toluene.

8. The method of claim 5 further characterized in that saidtransalkylation conditions include a temperature of from about 220 toabout 460 C.

References Cited UNITED STATES PATENTS CURTIS R. DAVIS, Primary Examiner

